1. Field Of The Invention
This invention relates to burner nozzles for burning petroleum products during well testing, and more particularly, to a burner nozzle having an adjustable orifice for flowing fluid into a swirl chamber.
2. Description Of The Prior Art
Burner nozzles in which petroleum products are burned, particularly to dispose of the products of oil well testing, are well known. The function of such nozzles is to atomize the petroleum products to facilitate burning. The atomization process occurs as the fluid is discharged from the nozzles and dispersed as tiny droplets. The smaller the droplet size, the better the atomization and the more complete the combustion process. This results in less fallout of unburned petroleum products. Finer fluid droplet size improves combustion by allowing adequate air to surround the droplet to complete the combustion process.
In many conventional burner nozzles, a substantially cylindrical swirl chamber is used having fixed orifice inlet ports. The inlet ports are perpendicular to the central longitudinal axis of the nozzle and are offset from the center line thereof. This geometry creates a swirl which produces a substantially conical fluid pattern as the fluid is discharged from the cylindrical swirl chamber. A burner nozzle of this type is disclosed in co-pending U. S. Pat. Application Ser. No. 07/350,105, assigned to the assignee of the present invention.
The orientation of the ports in these swirl chambers is such that each port jets into the one adjacent to it within the swirl chamber, and the fluid stream splits. One side of the fluid stream continues through the swirl chamber, and the other side is directed to the rear wall or back plate of the swirl chamber where erosion can occur, resulting in a loss of fluid energy and velocity.
A burner nozzle which addresses this erosion problem is disclosed in co-pending U.S. Pat. Application Ser. No. 07/431,050, also assigned to the assignee of the present invention. In the burner nozzle of Application Ser. No. 7/431,050, the swirl chamber has inlet ports which are disposed at an acute angle with respect to the longitudinal axis of the nozzle. This provides a gradual fluid entrance directed forward which reduces erosion in the rear wall or back plate of the swirl chamber and also reduces erosion in the nozzle portion of the conical swirl chamber. This design also has the advantage of allowing foreign matter and other debris to pass through the ports more easily than previous designs where the ports were perpendicular to the central axis. However, even with this improved swirl chamber configuration, the size of the inlet ports are fixed.
The quality of fluid atomization depends significantly on the velocity of the fluid into and out of the swirl chamber. The higher the fluid velocity, the smaller the fluid droplet size as the fluid is discharged. The velocity of fluid in nozzles with fixed orifice inlet portions depends on the fluid flow rate and number and inlet area of the orifices. Therefore, poor atomization at low flow rates is usually the result in order for good atomization to be obtained at higher flow rates.
When a well test is initiated, the fluid flow rate is unknown, and once initiated, the test may not be stopped easily to change the orifice size or number of nozzles. Inadequate orifice area may cause a back pressure upstream sufficient to require aborting the test. Excessive orifice area results in low swirl chamber velocity with the corresponding poor atomization and incomplete combustion. Since fluid flow rates typically vary during well tests fixed orifice inlet ports in swirl chambers present difficulties.
The present invention solves this problem by providing an adjustable orifice to admit fluid into the swirl chamber. The orifice size increases as the fluid pressure due to higher flow rates increases. Thus, the orifice size is determined by the flow rate, and the velocity of fluid in the swirl chamber remains high throughout a wide flow range so that good atomization and more complete combustion are maintained.